This application claims the benefit of a priority under 35 USC 119 to French Patent Application No. 0008870 filed Jul. 7, 2000, the entire contents of which are hereby incorporated by reference.
The present invention concerns the field of imaging, notably medical, and in particular mammography.
A radiology apparatus used, for example, in mammography, RAD or RF conventional radiology and neurological or even vascular (peripheral or cardiac) radiology is generally composed of: an X-ray tube and a collimator for forming and delimiting an X-ray beam; an image receiver, generally a radiological image intensifier and a video camera, or even a solid-state detector; and a positioner carrying the X-ray tube and collimator assembly on one side and image receiver on the other, movable in space on one or more axes. An example of such an apparatus is shown in EP-A-972,490.
An X-ray tube mounted, for example, in a medical radiology apparatus comprises a cathode and an anode, both contained in a vacuum-tight envelope, for electric insulation between those two electrodes. The cathode produces an electron beam which is received by the anode on a small surface constituting a focus from which the X-rays are emitted. An example of such an apparatus is shown in WO-A-97/44809.
Ordinarily, for the purpose of tracking down possible breast cancer, X-ray images are analyzed in order to deduce therefrom an estimate of the probability of a lesion in given areas. Then, in case of detection of a suspicious area, a practitioner takes one or more biopsies in order to have tissues available for an histological analysis. A problem with the mammograms is the difficulty in detecting and analyzing lesions in radiologically dense breasts, especially when they are not accompanied by microcalcifications, for the mammographic images are projection images, each pixel of which represents the cumulative attenuation of the beam across the total thickness of the breast.
An embodiment of the present invention seeks to reduce the number of biopsies which prove necessary and to increase the reliability of detection of lesions, by a high-quality visualization of breast lesions.
The method of examination of a breast, according to one aspect of the invention, comprises the steps of injection of a contrast medium in a breast to be examined, emission of an X-ray beam in the direction of the breast, taking a plurality of digital images of the X-ray beam after it has crossed the breast, and calculation of a representative image of the contrast produced in the tissues of the breast from the digital images.
The contrast medium can be injected in the blood vessels of a breast to be examined. The injection can be arterial or venous. Diffusion of the contrast medium is slower in the case of venous injection. The contrast medium can be iodine-based.
In an embodiment of the invention a first image is preferably taken before injection of the contrast medium.
In an embodiment of the invention at least one second image is taken after injection of the contrast medium.
In an embodiment of the invention, at least one second image is taken during a phase of heightened attenuation due to the contrast medium. Attenuation is understood to mean the diminution in number of X-photons when they cross the breast.
In an embodiment of the invention, at least one second image is taken after a phase of heightened attenuation due to the contrast medium.
In an embodiment of the invention, the second images are equally distributed in time. The second images are also called second image series.
In an embodiment of the invention, the second images are taken at shorter intervals during the phase of heightened attenuation due to the contrast medium than after the phase.
In an embodiment of the invention the number of second images can range between two and ten. In the second images, the gray level depends on the density of contrast medium in the breast.
In an embodiment of the invention a second image is preferably taken at the end of the heightened attenuation phase and a third image is taken a few minutes after the end of the phase.
In an embodiment of the invention the first image is advantageously subtracted from each of the second images. The subtracted images can be filtered spatially.
An embodiment of the invention is a radiology apparatus comprising means for injection of a contrast medium into a breast to be examined, means for emitting an energy beam, means for receiving the energy beam and sending an output a digital image representative of the incident energy beam, and means for processing for controlling the means for emitting and processing data from the means for receiving in order to calculate a representative image of the contrast produced in the cells of the breast from the digital images.
The means for processing is preferably capable of controlling the injection of a contrast medium after a first image is taken and before other images are taken. The means for processing can be capable of generating a representative image of the thickness of the contrast medium. The images can be converted into thickness images. A thickness image is understood to mean an image in which the gray level of the pixels depends on the thickness of the contrast medium.
An embodiment of the invention also directed to a computer program comprising means for providing program code for applying the steps of the method, when the program is working on a computer.
An embodiment of the invention is also directed to a storage medium capable of being read by a device reading the means for providing program code which are stored there and are suitable for use of the steps of the method, when the program is working on a computer.